Exercise to reduce your cancer risk, regardless of your weight

Regardless of what you weigh, moving your body can reduce the risk of cancer, according to new research.

At least one in three cancer cases can be prevented and researchers know that being physically active reduces your risk of certain cancers. Similarly, they know that the risk of certain cancers increases for the 63 per cent of Australian adults who are overweight or obese.

Exercise: It's important for all of us, regardless of our weight.Credit:iStock

While they know about the individual risk factors, researchers were unsure about how much one influenced the other to increase or decrease risk.

So, for the new study, the researchers from the Cancer Council Australia, looked at the BMI and activity levels of 8823 participants to explore their risk of developing prostate cancer, postmenopausal breast cancer, bowel cancer, ovarian cancer and uterine cancer.

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"What we looked at is the interaction between these factors – are the benefits of physical activity offset by BMI?," said study author Visalini Nair-Shalliker, a research fellow at Cancer Council NSW.

"We found they are independent of each other; if you're overweight or obese and exercise you reduce the risk -– weight loss is another issue."

"You are 53 per cent less likely to be diagnosed with uterine cancer compared with someone who is inactive," Dr Nair-Shalliker said.

She said it was unclear why the two factors were independent, particularly given that there is interplay between weight, exercise and your risk of cardiovascular disease.

"We are validating these findings in different data sets," Dr Nair-Shalliker said.

In the meantime, they do have some understanding of why being active is so important for our health and reduced risk.

Exercise is known to alter hormone metabolism, reduce oxidative stress, improve immune function, decrease inflammation, regulate insulin levels, and enhance lipid metabolism, all of which have an underlying role associated with cancer development, the Cancer Council said.

There is also understanding around the role of excess weight in increasing risk.

According to the American Society of Clinical Oncology: "The possible reasons that obesity is linked with cancer include: increased levels of insulin and insulin growth factor-1, which may help some cancers develop; chronic, low-level inflammation, which is more common in people who are obese and is linked with an increased cancer risk; higher amounts of oestrogen produced by fat tissue, which can drive the development of some cancers, such as breast and endometrial cancers; [and] fat cells may also effect processes that regulate cancer cell growth."

Dr Nair-Shalliker said our best chance of reducing our risk "across the board" is to get active and stick to a healthy, balanced diet (that is more vegetables, whole fruit, wholegrains, water and legumes and less processed meat, packaged foods, alcohol and sweetened drinks).

"Our findings are relevant to anyone who thinks they don't need to exercise for weight reasons," Dr Nair-Shalliker said, adding that they recommend at least 60 minutes of moderate or 30 minutes of vigorous physical activity a day.

"But if you are inactive, any level of physical activity will be beneficial."